BITTIUM CRASSTCOSTATUM. 525 



Remarkfi. — This interesting shell was also discovered ])y Mr. Bell when 

 examining Mr. Headlej's collection, where he noticed about 8 specimens of it. 

 I am not aware that it has been reported as recent except by Mr. Friele among 

 the mollusca of the North Sea Norwegian Expedition. That author remarks : 

 it may be easily distinguished from Admefe rlnduhi by its strongly angulated 

 whorls, which, when crossed by its standing ribs, become almost nodulous, and by 

 its smooth mammiform apex. 



Genus BITTIUM (continued from. Vol. J, p. 419). 

 Bittium crassicostatum (Etheridge and Bell). Plate XL VII, fig. 4. 



1898. CeritJiinm (Bittium) reticulatum, var. crassicostafa, A. Bell, Trans. Roy. Geol. Soc. Cornwall, 

 vol. xii, p. 143. 



Specific Characters. — Shell strong and solid, slender, subcylindrical ; whorls 

 convex ; suture deep and channelled ; spire slender, elongate, gradually tapering ; 

 ornamented by 5 or G rounded and projecting ribs continuous from apex to base, 

 except as interrupted by the suture, with wide interspaces, and by coarse spiral 

 ridges which cross the ribs ; mouth small, oval, angulate above, rounded below. 



Dimensions. — (Broken specimen) L. 12 mm. B, 3 mm. 



Distribution. — Not known living. 

 Fossil : St. Erth. 



Remarks. — Of this form Mr. Bell reports he obtained 3 or 4 specimens at St. 

 Erth. I think it may be regarded as a new as well as an interesting species, as 

 do MM. Dollfus and Dautzenberg. It is somewhat similar to the B. rohustum of 

 the Anglo-Belgian Crag described in Vol. I, p. 417, of this Memoir, but differs 

 materially from it both in form and sculpture. 



The specimen here figured is from the Warburton Collection in the British 

 Museum, where it is regarded as a variety of G. {Bittium) reticulatum. I prefer to 

 consider it specifically distinct. 



Bittium incile, Watson. Plate XLVII, fig. 7. 



1897. Bittium incile, Watson, Joiirn. Linn. Soc. (Zoology), vol. xxvi, p. 246, pi. xix, figs. 14, 14a. 



Specific Characters. — Shell small, solid, conical ; whorls 8—9, nearly flat ; spire 



elongate, regularly but slowly tapering upwards ; suture deep, channelled ; 



ornamented by 3 spiral rows of well-marked rounded nodules on each of the lower 



whorls, arranged also in longitudinal lines, the base having 3 sharp and strong 



ridges ; mouth ovate, angulate above. 



69 



